If ReduceExpressionsRule generates the same plan, the original plan stops triggering other rules

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Description

Calcite allows users to implement a customized RelOptPlanner#Executor to determine how a RexNode is reduced to another.

In some cases, the customized RelOptPlanner#Executor might decide not to do any reduction for a given RexNode (i.e., constExps2 and reducedValues are the same in [1]).

However, for these cases, Calcite is not aware of the new plan is equivalent to the old one, but just go ahead to force the Importance of the old/new plan as ZERO [2]. After the Importance becomes ZERO, the original plan stops triggering other rules